My ex-boyfriend have custody of our son, but he wants to cut his hair and im not ready, what should I do.

He and I share custody, but he has to get him every other weekend, and the last weekend that he was going to take him, he said to me that he would cut his hair, and he dont care that Im not ready to cut it and he doesnt even won't me to be there when he cut it, so I refused to let him see his son, and he called the police on me cause he has the right to his son for that weekend, am I in the wrong? I told him that he could get him, just don't cut his hair and he responded, "if he comes with me, im cutting his hair"